Objectives: I. To study sound lateralization behavior in normal monkeys. To develop a binaural stimulus generating and delivery system which allows precise stimulus control to each ear independently. To determine interaural intensity and phase angle difference thresholds for normal monkeys. II. To study the role of the auditory cortex and the forebrain commissures in interaural intensity and phase angle discrimination by the ablation method. III. To evaluate the role of the caudal medial geniculate nucleus and its cortical projection in visual and auditory pattern discrimination using the ablation method. IV. To study the role of species, reinforcement, learning sequence, and training method in the learning of auditory pattern discriminations by monkeys. V. To evaluate the role of auditory cortex in temporal auditory pattern discrimination in monkey by the ablation method. VI. To compare the role of the prefrontal cortex in cat and monkey in retention and relearning of auditory frequency and pattern discriminations. VII. To study cross model interaction between visual and auditory pattern learning by conditioned avoidance procedures. VIII. To examine the anatomical details of the thalamocortical portion of the monkey auditory system. IX. To compare the learning of auditory discriminations by monkeys subjected to total asphyxia at birth with that of monkeys born and reared in the same manner but not subjected to asphyxia.